Effects of pulse duration and areal density on ultrathin foil acceleration

Abstract

The influence of laser pulse duration and areal density of target in the interaction of a circularly polarized pulse with an ultrathin overdense foil is investigated. One-dimensional particle-in-cell simulation shows that with an appropriate laser-pulse rising front, the light pressure acceleration regime is effective even though the thin foil is transparent. As the laser intensity evolves, three stages in the acceleration process can be identified: at first the total reflection of the laser pulse, followed by partial reflection, and then near total reflection again due to the Doppler effect. The influences of the rising front of laser pulse and areal density of the ultrathin foil are investigated. It is found that an optimal laser pulse rising front exists for obtaining high (saturation) ion energy with the same laser energy within a short time. An optimal areal density also exists for obtaining the highest energy. For the same laser pulse, a higher areal density or a higher density with same areal density is more appropriate for obtaining a stationary state for making light pressure acceleration mechanism more effective.